Cushion dome



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CUSHION DOME Walter F. Malshary, Oakland, Calif., assignor to Malsbary Manufacturing Company, Oakland, Calif., a corporation of California Application April 29, 1955, Serial No. 504,819

6 Claims. (Cl. 138-26) The present invention relates to improvements in a cushion dome for a conduit, adapted for cushioning or damping pulsations in the conduit due to the starting and stopping of a flow of liquid through the conduit.

My invention was developed for use particularly in con nection with the Malsbary cleaning machine as illustrated, for instance in Patent No. 2,295,228, in which a liquid is pumped through a pipe line by means of a reciprocating pump against a head, but it may be used to advantage in any installation in which it becomes necessary to provide cushioning means for absorbing or damping shocks due to the starting and stopping of a flow of liquid through a pipe line or due to pump pulsations.

Heretofore, the common expedient for cushioning the shocks has been the well-known air dome in which a body of compressed air is confined with respect to the water passing through the line, so as to be subject to the pressure thereof. But these air domes usually have to be of considerable size as compared with the remainder of the installation, and are subject to the further handicap that the passing water or other liquid tends to entrain'the air, so that, as a rule, specific means have to be provided for continuously re-supplying the, air to the dome to compensate for the continuous loss of air.

In the present invention it is proposed to provide a simple cushioning means which does not depend upon the presence of a compressed body of air, and which can be built into a compact structure of relatively small proportions.

More particularly, it is proposed to provide a relatively small housing forming a chamber communicating with the liquid conduit, the housing having an opening to the atmosphere, and to use a heavy rubber cushion covering the opening and cooperating therewith in allowing the cushion to play or vibrate with respect to the opening in response to the pulsations in the conduit.

While the general idea of providing a heavy rubber cushion playing against an opening is not new, it is proposed in the present invention to provide certain improvements in the cushion, which tend to utilize a larger proportion of the cushion in absorbing pulsations, to

render the cushion more effective, to extend the life of the cushion and to overcome certain defects apt to develop in the cushion during extended use.

Further objects and advantages of my invention will be disclosed as this specification proceeds, and the new and useful features of my invention will be fully defined in the claims attached hereto.

The preferred form of my invention is illustrated in the accompanying drawing, forming part of this application, in which:

Figure 1 shows an axial section through my cushion dome; and

Figure 2, an end view of the same.

While I have shown only the preferred form of my invention, it should be understood that various changes or modifications may be made within the scope of the claims attached hereto, without departing from the spirit of the invention. I

Referring to the drawing in detail, my cushion dome comprises in its principal parts, a cylindrical housing 1 closed at both ends by means of plates 2, which in turn are provided with central openings 3, and two heavy bodies 4 of rubber disposed in opposite ends of the housing to serve as sealing elements for the openings.

The two heavy bodies leave a central space clear, as at 5, and this central space is connected to a conduit 6 by means of a short pipe 7.

The housing in its preferred form, is about five inches long, and has a diameter of approximately four inches. The openings in the opposite ends of the housing are approximately two inches in diameter, so as to leave rim sections 8 about one inch in width.

While these dimensions may be changed, of course, to suit various conditions, the proportions should be approximately maintained for best results.

In the drawing the cushion dome has been shown in duplex form, with two openings and two rubber bodies or sealing elements, but it would be feasible also to close one end of the housing completely, and to omit the corresponding sealing element, in which case the closed end could be moved much closer to the opposite sealing element.

It has been previously suggested to use a sealing element made in the form of a heavy flat disc lying against the end of the housing, the general idea being that the pump pressure would force a limited portion of the disc to bulge into and beyond the opening under pressure of the liquid, and would play in said opening in response to pump pulsation-s.

While this arrangement was generally satisfactory and performed the desired function, it was found, under actual working conditions, that certain difliculties developed. This was due to the fact that only a limited portion of the rubber partook of the vibratory movement, while the remainder was relatively inert, with the result that a certain fatigue developed in the material between the vibratory section and the inert material.

This again caused the vibrating section to gradually separate and tear loose from the inert material and to be blown through the opening by the pump pressure. There was also a certain tendency for the rim of the plain disc to separate from the wall of the housing and to break the seal.

In the present invention it is proposed to provide a rubber body of such a shape that the vibratory movement due to pump pulsations extends substantially through the entire body to avoid the fatigue element while at the same time the pump pressure tends to crowd the rim of the rubber body against the wall of the cylinder perfecting the seal.

It was also found, in actual practice, that the rubber flowing into and vibrating in the opening, had a' tendency to weaken along the rim of the opening,in spite of the fact that the edge of the rim was rounded, and in the present invention it is proposed to shape the body ofrubber in such a manner that no portion thereof flows into the opening and the entire vibratory .movement is confined to a space within the housing opposite the opening.

In accordance with these observations, the rubber body 4 is made substantially concavo-convex in form, presenting a convex inner face 10 to the liquid and a concave outer face 11 opposite the opening 3.

The body is cylindrical in form to fit against the inner face of the cylinder. throughout the entire area, While the concave section 11 is substantially co-extensive with the size of the opening, leaving a flat rim section 12 hearing on the inside face of the rim 8 of the housing. 1

The curves of the surfaces 10 and 11 may be approxi- Patented Oct. 1, 1957 The inner face 10 is made convex' mately concentric, although the curve 10 is preferably drawn to a slightly larger radius, as shown.

The rubber body is made of substantial thickness, sufficient to prevent the samefrombeing crowded .through the opening by pump pressure. In the form shown, it is:,approximately.one and one-quarter inches thick along the center line.

The bodyis composedof soft, yieldingrubber, so as to deform and vibrate in response to .pump pressure and pump vibrations. For pressures from30-150 pounds, it may have a durometer reading-of approximately 45, and for pressures from 150-25O pounds, a; durorneter reading of 50. t

In operation, the housinglis secured upon thepressure, conduit 6 in the usual manner, by means 'of the pipe 7, so as to allow the liquid from the-conduit to enter the space between the two rubber bodies.

, As the space or=chamber 5 is filled with liquid under pump pressure, the-pressure bears uniformly on each convex face 10 and converges, throughpractically the entire body of the rubber, upon the concave sectiomtending to straighten out the latter and to force the rubber material into the cavity. a As a result, the cavitywill substantially disappear, and the rubber material will be crowded into an approximately straight plaue against the opening 3.

As the pump is made to operate, the pump pulsations will act onthefaces 10:01? the rubber bodies, producing similarpulsations throughout the bodies, and causing the faces .11 to vibrate toward and away from the openings for absorbing or damping the pump pulsations.

It will be noted that in the shock-absorbing action practically all the rubber material takes part in the vibratory movement and that there is little material remaining inert. Since thus the stresses are distributed over a wider area, there will'beless fatigue, and a better absorption of pulsations.

The pressure of the liquid tends to straighten out the curvature of the inner face 10 of 'each rubber body, and there is a definite tendency for the rubber to expand toward the side wall of the cylinder for improving the sealing action.

Since the rubber material at the concave section does not actually enter the opening 3, but merely flattens toward'the opening, there is little danger of the rubber cutting against the rim of the opening, although it is advisable, of course, to round out the near edge, as shown at 12.

I claim:

l. A cushion dome for a conduit having means for pumping a liquid thcrethrough under pressure, comprising a housing having a chamber communicating with the conduit and having an unrestricted opening in the wall thereof and leading to the atmosphere, and a confined sealing member within the chamber and normally hearing upon therim of the opening under pressure of the liquid for sealing the opening, the sealing member being in the form of a-solid body of rubber material having a convex end facing 'the liquid and a concave end section facing the opening, and the concave endsection and the opening being substantially coextensive and bearing relation in size to the thickness of the body to cause the concave section toplay toward andaway from the opening in response to pump vibrations.

2. A cushion dome for a conduit having means for pumping a liquid therethrough under pressure, comprising a housing having .a'chamber communicating with the. conduit and having an unrestricted opening in the wall thereof and leading to the atmosphere and a confined sealing member withinthechamber and normally bearing upon the rim of the opening underpressure of the liquid for sealingthe opening,the sealing'm'emberbeiug in'the form of a solid body of rubber material having a convex end facing the liquid and a concave end section facing the opening, and the concave end section and the opening being substantially coextensive and bearing relation in size to the thickness of the body to cause the concave section to play toward andaway from the opening in response to pump vibrations, and the convex end being larger than the concave section and substantially concentric therewith to cause pressure brought to bear on the convex end to converge upon the concave section substantially along radial lines.

3. A cushion dome for a conduit having means for pumping a liquid therethrough under pressure, comprising a housing having a chamber communicating with the conduit and having an unrestricted opening in the wall thereof and leading to the atmosphere, and a confined sealing member within the chamber and normally bearing upon the rim of the opening under pressure of the liquid for sealing the opening, the sealing member being in the form of a solid-bodyof rubber material having a convex end facing the liquid and a concave end section facing theopening, and the concave end section and the opening being substantially coextensive and bearing relation in size to the thickness of the body to cause the concave section to play toward and away from the opening in response topurnp vibrations, and the convex end being larger than the concave section and substantially con- 7 centric therewith to cause pressure brought to bear on the convex end to converge upon the concave section substantially along radial lines, with the rim engaging portion of the body sutficicntly wide to cause the pressure brought to bear on the convex face to expand a rim portionof the body against the Wall of the structure for effecting a'tight seal between said rim and said wall.

4. A cushion dome for a conduit having means for pumping a liquid therethrough under pressure, comprising a housing having a chamber communicating with the conduit and having an opening in the wall thereof and leading to the atmosphere, and a confined sealing member within the chamber and normally bearing upon the rim of the opening under the pressure of the liquid for sealing the opening, the sealing member being made of solid rubber material and having a convex end facing the liquid and a concave section facing the opening, the convex end being co-extensive with the cross-section of the chamber, and the concave section being coextensive with the opening, and the convex end and the concave section being substantially concentric to cause pressure brought to bear on the convex end to converge upon the concave section substantially along radial lines with the opening made of considerable size as compared with the crosssection of the housing so as to subject substantially the entire body of the sealing member to the converging pressure of the liquid, while leaving a rim section of the sealing member operable by the liquid pressure to expand against the confining means for perfecting the seal.

5. In a device of the characterdescribed, a heavy solid cylindrical body of rubber material having a flat rim section at one end thereof, with a concave section inside the rim and being convex at the opposite end throughout the Width thereof, the Width of the rim section being substantially, equal to the radius of the concave section and the thickness of the body along the centerline being approximately equal tosaid radius.

6. A cushion dome for a conduit having means for pumping a liquid therethroughunder pressure, comprising a cylindrical housing having a chamber communicating with the conduit and having an opening in one end wall thereof and leading to the atmosphere, and a cylindrical sealing member fitting within the chamber and having at one end a flat rim section bearing on the rim of the opening anda concave section facing the opening, the said member having a convex opposite surface facing the liquid and being made of rubber material of sufiicient thickness with respect to the opening to prevent the liquid from forcing the member through the opening while allowing the concave section to flatten toward the opening in response to pump pulsations.

References Cited in the file of this patent UNITED STATES PATENTS Whitney Apr. 30, 1907 Martin Oct. 1, 1940 Ragland Ian. 22, 1952 Lee May 27, 1952 

